Breast cancer is a complex disease, and recent research shows that obesity plays a bigger role than previously thought, especially when it comes to early-onset breast cancer. While we’ve long understood that obesity increases breast cancer risk in post-menopausal women, new studies are revealing just how much it impacts younger women—particularly Black women.
According to a cohort study published in JAMA, women who struggle with obesity, especially Black women, are more frequently diagnosed with breast cancer compared to their white counterparts. Black women with obesity are also at a significantly higher risk for early-onset breast cancer and are more likely to be diagnosed with two aggressive molecular subtypes: luminal A and triple-negative breast cancer. This is especially alarming because triple-negative breast cancer is known to be particularly difficult to treat.
Obesity and early-onset breast cancer
“Traditionally, we’ve known that obesity increases breast cancer risk in post-menopausal women, but today, we understand that early-onset breast cancer risk is also heightened in younger women, especially those with BRCA1/2 mutations,” Dr. Melissa D. Fana, a director of women’s health at Perlmutter Cancer Center at NYU Langone Long Island Breast Surgery Associates, tells Flow Space. “In addition, certain molecular subtypes—like luminal A and triple-negative—are more strongly associated with obesity.”
The JAMA study provides a clearer picture of the disparities Black women face. Among the 1,085 patients, 30.6% were Black, with a median age of 58, and 69.4% were white, with a median age of 63. Nearly half of all participants were obese, with Black women disproportionately affected.
Fana points out that these findings highlight the need to pay closer attention to obesity’s role in breast cancer, especially since Black women experience higher rates of obesity compared to white women.
“There are multiple factors affecting obesity rates among Black women, and this is linked to the higher rates of luminal A and triple-negative breast cancers we’re seeing,” Fana notes. “We also have to recognize the diagnostic challenges obesity creates.”
Fana explains that while it’s often assumed that detecting abnormalities in less dense breasts would be easier, the reality is quite different. Excess adipose tissue can actually make it harder to spot cancers or fully assess the extent of the disease on mammograms. This can result in more false negatives and delays in diagnosis.
But the problem doesn’t stop at diagnosis.
Racial disparities in diagnosis
Recent research has been exploring the gut microbiome—the ecosystem of microorganisms in the intestines—and how imbalances or dysfunction in this environment may contribute to the development of breast cancer.
“The low-grade chronic inflammation caused by obesity can negatively impact the microbiome, as well as potentially cause cellular damage in healthy breast tissue, which can increase the risk of breast cancer,” Dr. Anne Peled, a breast cancer surgeon based in San Francisco, says.
In addition, treatment outcomes for obese women with breast cancer are often worse, and race is a significant factor in these disparities. Research shows that Black women, who are more likely to be diagnosed with obesity-related breast cancers, like triple-negative and luminal A, face additional challenges. These challenges include delayed diagnoses, lower access to quality care and higher rates of late-stage diagnoses, all of which contribute to poorer survival rates.
“There’s more evidence to show that weight loss helps reduce the chance of getting post-menopausal breast cancer, but other factors like regular exercise and adhering to a more plant-based diet that can go along with weight management programs do reduce the risk of breast cancer in younger women,” says Peled.
Looking ahead
The findings from this study suggest that obesity is more than just a risk factor—it’s a major contributor to the disparities in breast cancer diagnosis and outcomes between Black and white women. Addressing this issue will require more than just awareness. Doctors need to improve diagnostic tools for obese patients, invest in further research and ensure access to care for Black women.
“We have to probe further into the mechanisms driving these cancers and continue educating and supporting our vulnerable populations,” says Fana. “That’s how we can make real change.”
For now, it’s clear that obesity not only influences the timing of breast cancer diagnosis but also the specific type of breast cancer diagnosed—and Black women are facing the brunt of these disparities. Understanding the link between obesity and breast cancer is just one step toward addressing healthcare inequities.